Technical Abstract:
The Norfolk loamy sand of the SE Coastal Plain often has poor physical properties because it contains a cemented subsurface hard layer that restricts root development and infiltration. Physical properties are often improved by adding amendments. Organic residue and/or polyacrylamide (PAM) were mixed into a blend of 90% E horizon and 10% Ap horizon (to assure microbial activity) of a Norfolk soil. We hypothesized that incorporation of these amendments would minimize re-cementation of soil particles and improve physical properties. Pots containing 450 g of soil and amendment mixtures were incubated for 90 d at a 10% (w/w) basis. The pots were leached twice with about 1.35 pore volumes of deionized water at 50 and 80 days. After leaching and equilibration to a stable water content, soil strength was measured with a 5-mm diameter flat-tipped bench-top pemetrometer. Compared to the control, soil mixtures with organic residue had lower bulk densities and strengths, while mixtures containing PAM had higher bulk densities and strengths. In mixtures with both amendments, the effect of organic matter on bulk density and strength seemed to dominate over PAM. Both organic matter and PAM treated soils held more water against drainage and/or evaporation than the control. Organic matter appeared to improve all physical properties, and though PAM increased soil water holding capacity, it is unclear whether it improved this soil's physical properties or not.